Listening #17

Lots of amplifiers come through these doors, and most of them have one thing in common: They're heavier than the boxes meant to contain them. A lot heavier. In fact, at least half the cartons I see in this line of work couldn't last more than two or three trips before giving way to their weighty contents—rather like the seats of some audiophiles' dungarees.

By contrast, a DNM 3-C preamplifier weighs nine times less than the simple yet nicely made wooden crate that contains it—and which, as I observed in last month's column, is meant to be returned to the new owner's DNM dealer, from whence it will return to its factory in Switzerland, to be used all over again. (But, as an American, I advise DNM to offer a deposit refund, lest we start to see their amplifier crates littering US roadsides along with all those Mountain Dew bottles and empty Skoal tins.)

As you also know from last month's "Listening," literally everything in the 3-C that isn't meant to conduct electricity is made of plastic. For that reason, and because the 3-C is not one whit larger than a domestic stereo preamplifier needs to be, most adults could easily lift this product and its crate in one hand. Which I did now and then, to show off. A complete DNM system—everything between the source at one end and the loudspeakers at the other—can be contained in two of those small wooden crates.

Actually, there's a bit more to it than that, as I recently discovered when DNM's American distributor (footnote 1) sent me a system to try: A third, smaller carton contained a neat-looking Wonpro outlet strip (modified and sold by Eichmann as an "eXpress Power Strip" and imported by Audiophile Systems Ltd.). DNM encourages users to plug their entire system into one AC strip, to keep the electrical grounds for all the components at the same potential. (The difference in series resistance between a home's ground and neutral runs creates the possibility of a slight, and slightly different, voltage at the ground contact of each AC outlet.)

I shouldn't have been surprised that DNM's Denis Morecroft, a pioneer in the application of star grounding to domestic audio, would advise such a thing. Nor should I have been shocked to see that the Wonpro contained solid-core wire and smallish metal contacts—and was otherwise plastic, through and through.

I installed the Wonpro strip in my listening room, then opened up wooden crate No.1. Nestled inside the styrene foam partitions were the 3-C preamp and its separate power supply (a $3495 package), along with all the necessary DNM interconnects and a solid-core AC cable. Like Naim Audio, that other company that stresses proper connection impedances and grounding schemes, DNM uses five-pin DIN sockets for all signal inputs and outputs. Unlike Naim, DNM keeps output signals and DC voltages separate from one another, rather than routing them alongside one another in a single umbilical. Also unlike Naim, DNM's DINs have plastic locking collars rather than the standard metal ones.

Two solid-core interconnect cables supplied with my review sample were terminated with a male DIN at one end and a pair of RCA plugs at the other, for line-level source components. A DIN-to-RCA socket adapter, also fashioned from DNM solid-core cable, allowed me to connect my Naim Aro tonearm's signal cable directly to the 3-C's moving-coil phono input. Of course, a real DNM owner would most likely reterminate his or her tonearm cable with a DIN plug, thus avoiding the need for such an adapter.

There are three power-supply sockets on the back of the DNM 3-C, each addressing a different portion of the preamp's gain, buffering, and equalization circuitry. (The 20-pin sockets divide down even further between different DC applications, as they do between the left and right channels.) The entry-level Primus supply—a fairly straightforward thing comprising a toroidal transformer, four diodes, two slit-foil smoothing caps, and two voltage regulators—has only a single DC output cable, and its three 20-pin plugs are connected in series. With DNM's more sophisticated power supplies, available as extra-cost options, each socket gets its own individual cable and supply circuitry. My loaner was equipped with the Primus, and although previous experiences with other brands (ie, Naim) would lead me to expect audibly better performance with higher-cost power-supply options, I can't say for sure till I've tried.

DNM PA3-S power amplifier
With the DNM 3-C set up on its own Mana Reference Stand and the Primus power supply sitting on the hardwood floor underneath, I turned my attention to crate No.2. That one contained the DNM PA3-S 23Wpc power amplifier ($4695), plus its own outboard power supply and solid-core AC cable.

The PA3-S is twice as heavy as the 3-C preamp, yet still exponentially lighter than most other power amps. Like the 3-C, the PA3-S is built into a smoked-Plexiglas case about the size of a table radio. Heatsinks protrude some distance from the front—as much to minimize the deleterious effects of eddy currents as to maximize cooling efficiency—and the rear panel is taken up with input and output sockets. The former are DINs, the latter a series of gold-plated contacts meant to take 2mm pins only, with built-in provisions for triwiring. (The DNM website suggests that owners of single-wired systems can improve their amps by desoldering the contacts for bi- and triwiring. I didn't try that with my single-wired Quads or Lowthers, mostly because I don't like screwing around with a soldering iron inside things that don't belong to me.)

Only a portion of the amplifier's power supply is housed externally: The diodes, regulators, and a pair of T-Network reservoir caps are fitted to a separate board inside the amp itself, while the chunky toroidal transformer lives outside, connected to the amp with a three-pin XLR connector. When I pried open the external box to see what I could see, the most noticeable thing was a big sticker on the trannie with the word "passed." Now, unless there's a roughly equal chance of opening one of these things and seeing the word "failed," the English major in me must criticize DNM for redundancy. Denis, meet Tim. Tim, meet Denis. [Baffled readers should read the conclusion of AD's EAR 890 review in April, p.173——Ed.]

Setup was straightforward and mostly driven by common sense: I kept trannies away from low-level signals, made sure cables crossed one another at right angles, and so forth. Except for that amp-to-transformer run, all of DNM's cabling is light and flexible. It's attractive, too, with its color combination of clear, red, and a shade of blue that can be described only as French. Except for the two (non-acrylic) plastic boxes for the remote power supplies, which are borderline, the quality of manufacturing and assembly is extremely high.

The preamp's motherboard, with its precisely shaped traces and clever star ground routing, really has to be seen to be appreciated. Ditto the power amp's carefully layered 3D boards and neat row of ceramic heatsink interfaces. Every position of every part has been carefully thought out, and every solder joint has been made with great precision. Signal traces are sized for the job they're asked to do—nothing is larger or smaller than it needs to be—and all connectors are selected for engineering rather than jewelry values, which is all but unheard of in this industry. Yes, the DNM amp and preamp are small, light, and look unusual, but they also exude a deadly seriousness. DNM gear is Playhouse 90 or I, Claudius in a land where most everything else is Bozo's Big Top.

And where did they get all those cool acrylic screws?

Music from both channels?
With my Quad ESL-989s warmed up and waiting, I switched on the two power supplies, preamp first. I knew from reading DNM's literature that the preamp is meant to be completely dark when music is playing, and that was so. (Activating Mute illuminates that button, as well as a circle of LEDs directly beneath the central ground point on the motherboard—a lovely touch.) I also expected that the amplifier's heatsinks would warm up fairly quickly, then cool down a bit once things had stabilized, and that, too, was so.

But I expected to hear music out of both channels, and that was not so. After performing that most basic of hi-fi system tests—swapping the interconnects left for right, then listening for whether the problem moved or stayed in the same channel—I narrowed the fault to the preamp, and went on a loose-board hunt. I found two. (Apart from the motherboard, a DNM preamp that's configured for phono use will have at least six plug-in boards, with a great many gold-plated pins.) I gently re-seated everything, then settled back for a trouble-free listen.